Aircraft actuator piston

ABSTRACT

A piston ( 16 ) comprising a shaft ( 60 ), a head ( 62 ) and a transition corner ( 64 ) therebetween. The piston ( 16 ) can be formed from a two-piece blank with an inertia-welded interface ( 36 ) joining the pieces. The interface ( 36 ) does not intersect the transitional corner ( 64 ) and is instead positioned radially outward therefrom.

RELATED APPLICATION

This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 60/947,461 filed on Jul. 2, 2007. The entire disclosure of this provisional application is hereby incorporated by reference. If incorporated-by-reference subject matter is inconsistent with subject matter expressly set forth in the written specification and drawings of this application, the present disclosure governs to the extent necessary to eliminate indefiniteness and/or clarity-lacking issues.

GENERAL FIELD

A piston for use in an aircraft actuator to motivate movement of a control surface.

BACKGROUND

An aircraft can comprise an actuator for selectively moving a control surface, such as a spoiler, during flight. Control-surface movement can be motivated by an actuator comprising a piston and an associated cylinder barrel containing working fluid (e.g., oil). The piston can comprise a shaft, a head and a transitional corner therebetween. One end of the shaft is connected (either directly or through linkage) to the control surface and the other end of the shaft is connected to the piston head. The piston head is positioned within the barrel and, in response to fluid pressure, slides to thereby push or pull the piston shaft in a linear fashion.

SUMMARY

A piston is provided that provides both stress-free-interface features found in single-piece-piston designs (wherein the entire piston is machined from a solid cylindrical blank) and material-saving advantages afforded by two-piece-piston designs (wherein the shaft blank need not be as radially wide as the head blank). The piston is formed from a two-piece piston blank in such a manner that the interface does not intersect with the transitional corner between the shaft and the head. In two-piece-piston designs, this transitional corner is often the area of maximum axial and bending stress as the device performs its pushing and pulling motions. By locating the interface outside this high-stress area, a stronger piston can be provided with conventional materials and without resorting to a single-piece design.

Additionally or alternatively, the pieces of the piston blank can be inertia welded together at the interface. Specifically, for example, the two blank pieces can be rotated relative to each other to generate sufficient heat to energy to plasticize the pieces at the interface and thereby cause consolidation. The formation of the interface joint is autogenous and does not require a “filler” material as necessary in conventional welding processes.

One significant advantage of inertia welding is that the blank pieces can be made from dissimilar materials (e.g., different metals). For example, the blank piece forming the piston's shaft can be made of stainless steel. And the blank piece forming the outer surface of the piston's head can be made of galling-resistant alloy. By making the piston-head material inherently resistant, conventional (and expensive and troublesome) coatings and platings can be eliminated.

These and other features of the piston blank, the blank pieces, and/or the piston are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail certain illustrative embodiments, these embodiments being indicative of but a few of the various ways in which the principles may be employed.

DRAWINGS

FIG. 1 is a schematic drawing of an aircraft having a control surface for selective movement during flight.

FIGS. 2A-2C are schematic drawings of an actuator wherein a piston motivates movement of the control surface.

FIGS. 3A-3G are various views of a blank (and pieces thereof from which the piston can be formed.

FIGS. 4A-4B are side and sectional views of the piston.

DESCRIPTION

Referring now to the drawings, and initially to FIG. 1, an aircraft 10 is shown having spoilers 12 for selective movement during flight. As shown schematically in FIGS. 2A-2C, this movement can be facilitated by an actuator 14 comprising a piston 16 and an associated cylinder barrel 18, along with linkages 20 and 22.

The piston 16 can be formed from a two-piece blank 30 such as is shown in the 3^(rd) set of drawings. The blank 30 can comprise a stem piece 32 and a cap piece 34 joined together at an interface 36. The stem piece 32 need not be as radially wide as the cap piece 34.

The stem piece 32 can have an elongated generally cylindrical shape comprising a cap-side axial end 40 and an opposite axial end 42. An interfacing projection 44 is defined by an exterior wall 46 that tapers towards and to the axial end 40. The remaining (“non-interfacing”) portion 48 of the stem piece 32 can be non-tapering.

The cap piece 34 can have a generally disk-like shape with a stem-side axial face 50 and an opposite axial face 52. An interfacing pocket 54 is defined by an interior wall 56 that tapers away from its stem-side face 50. A basement 58 (or sub-pocket) can be positioned at the floor of the pocket 54 if, for example, it was used during fabrication of the cap piece 34.

The stem's projection 44 is positioned within the cap's pocket 54 thereby providing the interface 36 between the exterior wall 46 and the interior wall 56. The stem piece 32 and the cap piece 34 are joined together at this interface 36, preferably by inertia welding. If the pieces 32 and 34 are joined by inertia welding, the blank 30 (and/or the piston 16) can be characterized by the absence of filler material in the interface 36 and/or by the absence of mechanical connections (such as nuts, bolts, etc.).

The stem piece 32 and the cap piece 34 can be made from dissimilar materials (e.g., dissimilar metals). For example, the stem piece can be made stainless steel and/or the cap piece can be made from a gall-resistant alloy (e.g., CU—Ni—Sn alloy, BeCu alloy, Nitronic 60 alloy). While in the illustrated embodiment, the pieces 32 and 34 are essentially solid (except for the pockets 54/56 in the cap piece 34), cavities or grooves could be formed in the blank pieces prior to joining them together.

The interface 36 (and thus the walls 46 and 56) can have a truncated-cone shape. The taper angle can be, for example, between 20° and 40°, and/or between 25° and 35°, and/or about 30°. This conical geometry may be compatible with inertia welding steps and/or of the placement of the interface 36 in the completed piston 16.

Referring now to FIGS. 4A and 4B, the piston 16 formed from the piston blank 30 is shown. The piston 16 comprises a shaft 60, a head 62, and a transitional corner 64 therebetween. The transitional corner 64 can be considered the stress-critical area of the piston 16 and, significantly, the interface 36 does not intersect this area. Instead, in the illustrated embodiment, the interface 36 is positioned radially outward from the corner 64 on a ledge 66 projecting outward therefrom.

The piston shaft 60 is formed (e.g., machined) from the non-interfacing portion 48 of the stem piece 32. The piston head 62 is formed (e.g., machined) from the stem's projection 56 and the cap piece 34. The transitional corner 64 is formed only by the stem piece 32 and the outer radial surface of the head 62 is formed only by the cap piece 34. Interior cavities 70, grooves 72, attachment nubs 74, and/or mounting studs 76 can also be formed (e.g., machined) into the pieces 32 and 34.

Although the aircraft 10, the control surface 12, actuator 14, the piston 16, the blank 30, the pieces 32/34 and/or related methods and steps have been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. For example, the actuator 14 need not be used in an aircraft, the piston 16 need not motivate movement of a control surface, and/or the piston 16 need not be used in an actuator (and/or with a barrel cylinder). In fact, the piston 16 would be welcomed in many other applications as its advantages transcend aircraft and/or actuator settings.

In regard to the various functions performed by the above described elements (e.g., components, assemblies, systems, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application. 

1. A piston blank comprising: a stem piece having a cap-side axial end and a projection defined by an exterior wall that tapers to its cap-adjacent axial end; and a cap piece having a stem-side axial face and a pocket defined by an interior wall tapering from its stem-adjacent axial face; wherein the stem projection is positioned within the cap pocket thereby providing an interface between the projection-defining exterior wall and the pocket-defining interior wall; and wherein the stem piece and the cap piece are joined together at this interface.
 2. A piston blank as set forth in claim 1, wherein the stem piece and the cap piece are inertia welded together at this interface.
 3. A piston blank as set forth in claim 2, wherein the stem piece and the cap piece are made from dissimilar materials.
 4. A piston blank as set forth in claim 3, wherein the stem piece and the cap piece are made from dissimilar metals.
 5. A piston blank as set forth in claim 4, wherein the stem piece is made from stainless steel.
 6. A piston blank as set forth in claim 5, wherein the cap piece is made from a gall-resistant alloy.
 7. A piston blank as set forth in claim 2, wherein the interface has a truncated-cone shape.
 8. A piston formed from the piston blank set forth in claim 1, the piston comprising: a shaft, a head, and a transitional corner therebetween; wherein: a shaft formed from a non-pocketed portion of the stem piece; a head formed from the cap-interfacing projection of the stem piece and the cap piece; and a transitional corner between the shaft and the head; wherein the interface does not intersect with this transitional corner.
 9. A piston as set forth in claim 8, wherein the transitional corner is formed only by the stem piece.
 10. A piston as set forth in claim 9, wherein the head forms a ledge projecting radially outward from the transitional corner and surrounding the shaft, and wherein the interface intersects with the ledge radially outward from the transitional corner.
 11. A piston as set forth in claim 10, wherein the stem piece and the cap piece are inertia welded together at the interface.
 12. A piston as set forth in claim 11, wherein the stem piece and the cap piece are made from dissimilar materials.
 13. A piston as set forth in claim 12, wherein the stem piece and the cap piece are made from dissimilar metals.
 14. A piston as set forth in claim 13, wherein the stem piece is made from stainless steel.
 15. A piston as set forth in claim 13, wherein the cap piece is made from a gall-resistant alloy.
 16. A piston as set forth in claim 11, wherein the interface has a truncated-cone shape.
 17. A method of making a piston from the piston blank set forth in claim 1, said method comprising the steps of: forming a shaft from a non-pocketed portion of the stem piece; and forming a head from the stem projection and the cap piece; wherein said forming steps are performed such that the interface does not intersect with a transitional corner between the shaft and the head.
 18. A method as set forth in claim 1, wherein said forming steps comprise machining the stem piece and the cap piece.
 19. A method as set forth in claim 18, wherein said forming steps are performed such that the head forms a ledge projecting radially outward from the transitional corner and surrounding the shaft, and wherein the interface intersects with the ledge radially outward from the transitional corner.
 20. An aircraft hydraulic actuator comprising the piston set forth in claim
 8. 